1. Field of the Invention
The present invention relates to a process for producing a multilayer molded article in which a surface of a thermoplastic resin substrate is entirely or partly laminated with a skin material.
2. Description of the Related Art
Multilayer molded articles in which-a skin material is laminated on a surface of a thermoplastic resin substrate have been used in a wide variety of fields such as interior parts of automobiles (for example, door trims and instrument panels), and interior and exterior parts of household electric appliances.
As methods for producing such multilayer molded articles, there have been known a method in which a molded article (substrate) obtained by previously forming a thermoplastic resin into a desired shape by a variety of methods such as injection molding is laminated and stuck with a skin material using adhesives or the like, a method using an injection press method, as disclosed in Japanese Patent Publication Kokoku No. 83058/1993 (JP-B-05-83058), in which a skin material is supplied between a pair of a female and a male mold halves, a molten thermoplastic resin is thereafter supplied, and the skin material is then laminated on the surface of the molten thermoplastic resin in parallel with forming the molten thermoplastic resin into a desired shape by means of clamping the mold halves, and so on.
However, the former method includes complex steps and has problems on human bodies and environment caused by solvents contained in the adhesives. The latter method has an advantage that forming a substrate and laminating a skin material onto the substrate can be carried out simultaneously, but there is a problem that texture of the skin material in the molded article obtained is deteriorated because a molding pressure is applied to the skin material under the same condition as that of the resin portion. Particularly, in a case where a fabric skin material with raising is used as the skin material, the raising falls down due to the pressure in mold clamping and the appearance is seriously deteriorated. In a case where a skin material backed with a foamed layer is used, there is a problem that the foamed layer is crushed by the heat and the molding pressure in the mold clamping, so that a cushion property is deteriorated.
Under these circumstances, the present inventors have studied to develop a process for producing a multilayer molded article wherein the advantage of the injection press molding method that a surface of a substrate can be laminated entirely or partly with a skin material in parallel with forming the substrate is utilized, and even in a case where a fabric skin material with raising or a skin material backed with a foamed layer is used, deterioration in an appearance and in a cushion property caused by falling down of the raising and crush of the foamed layer never occurs. As a result, they have accomplished the present invention.
In one of its broader aspects, the present invention concerns a process embodiment for the production of a multi-layer molded article in which a surface of a thermoplastic resin substrate is partly or entirely laminated with a skin material. This embodiment uses a mold including a pair of female and male mold halves. This process embodiment includes supplying the skin material to a predetermined position between the female and male mold halves while they are in an open state; supplying a molten thermoplastic resin between the skin material and a molding surface of any of the mold halves (male and female), clamping the mold halves together after or while supplying the molten thermoplastic resin, conducting primary cooling of the molten thermoplastic resin in the mold, moving a part or a whole of a mold half, wherein the part or the whole of the mold half has a molding surface contacting the skin material, relative to a surface of the skin material to create a gap between the surface of the skin material and the part or the whole of the molding surface of that mold half; conducting secondary cooling of the molten thermoplastic resin while maintaining the relative position of the male and female mold halves following the just described movement, opening the mold halves after the molten thermoplastic resin has solidified, and thereafter removing the molded article from the mold.
Another process embodiment concerns the production of a multi-layered article in which a surface of a thermoplastic resin substrate is entirely laminated with a skin material. In this process, a mold including a pair of mold halves (a male mold half and a female mold half) involves supplying the skin material to a predetermined position between the female and male mold halves, the mold halves being in an open state relative to one another. A molten thermoplastic resin is supplied between the skin material and a molding surface of any one of the mold halves (the female and male mold halves). The mold halves are clamped together after or while supplying the molten thermoplastic resin. The molten thermoplastic resin in the mold is subjected to a primary cooling treatment. The two mold halves are opened relative to one another to create a gap between the surface of the skin material and the whole of a molding surface of at least one of the mold halves. The molten thermoplastic resin is suspected to a secondary cooling treatment conducted while maintaining the position of the mold halves with the just described gap therebetween. The mold halves are opened after solidification of the molten thermoplastic resin and the molded article is removed from the mold.
The present invention includes yet another process embodiment for the production of a multi-layer molded article in which a surface of a thermoplastic resin substrate is partly laminated with a skin material. This process also uses a mold including a pair of a male and female mold halves. It also includes a part of a mold surface corresponding to a skin material-laminated surface of the molded article which comes into contact with the skin material, being composed of a movable block which can slide forward and backward in a mold opening/closing direction in the mold. This process embodiment includes supplying the skin material to a predetermined position between the female and the male mold halves while they are in an open state. A molten thermoplastic resin is then supplied between the skin material and a molding surface of the mold half having no movable block. The mold halves are clamped together after or while supplying the molten thermoplastic resin. The molten thermoplastic resin in the mold is subjected to a primary cooling. The movable block which contacts the skin material in the mold half is retracted to create a gap between a surface of the skin material and a molding surface of the movable block. The molten thermoplastic resin in the mold is subjected to a secondary cooling while maintaining the relative position of the mold halves with the just described gap. The mold halves are opened after the resin has solidified and the molded article is removed from the mold.
With respect to the process embodiments described, the gap created between the female and male mold halves can be a half or more of the difference in thickness between the unprocessed skin material prior to molding and the skin material being under compression when the mold halves are clamped together after or while supplying the molten resin.
The skin material can, if desired, be a fabric skin material having a raised surface.
Throughout this specification and the claims which follow, unless the context requires otherwise, the word xe2x80x9ccomprisexe2x80x9d, and variations such as xe2x80x9ccomprisesxe2x80x9d and xe2x80x9ccomprisingxe2x80x9d, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integer or step.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.